The invention relates to a method for the linearization of a frequency modulated continuous wave (FMCW) radar device.
With FMCW radar devices, phase errors occur in the reception signal, as the result of a not strictly linear characteristic in a transmission frequency of an FMCW radar device. This results in a loss of accuracy in the evaluation of the signal.
In this case, various methods are known for linearizing an FMCW radar device. For example, one known method discloses a method wherein a delayed transmission signal is generated via an optical delay line having a defined running time. In this case, the delayed transmission signal is mixed with the non-delayed transmission signal. Thus, it is possible to determine the deviation from the ideal linear characteristics. In particular, the disadvantages of this method are the great amount of construction effort, expense and the age-related clouding of the optical components.
In addition, it is also known to generate a signal function that can be predetermined, such as a linear characteristic via a digital direct synthesis (DDS) system. However, a disadvantage of this system is that there is a large construction effort and expense associated with this cost intensive structure.
An FMCW radar system having linear frequency modulation is known from German Patent DE 4104792 A1. In this system, there is an oscillator that generates a ramp-shaped modulated signal having a modulated oscillation frequency, which is emitted by an antenna. A monitoring and control unit determines the deviation of the measured modulated oscillator frequency of a signal reflected from an object via a Hilbert transformation using a linearized reference value. In this case, a phase deviation can be determined from the deviation that has been determined.
From this deviation, a correction signal is generated, which is passed to the oscillator, whereby the oscillation frequency is modified in accordance with the predetermined reference values. A disadvantage of this system is that this involves a great construction effort, which is cost intensive, since additional components are required.